Method and device for operating a smelting reduction process

ABSTRACT

In a method and a device for operating a smelting reduction process, at least part of an export gas from a blast furnace or a reduction unit is thermally utilized in a gas turbine and the exhaust gas of this gas turbine is used in a waste heat steam generator to generate steam. The remaining part of the export gas is fed to a CO 2  separation apparatus, the tail gas thereby obtained being fed to a waste heat steam generator and burned for additional steam generation. The combustible components of the tail gas are sent for thermal utilization in a steam generator, so that the overall energy balance of the thermal use of the export gas is improved. In addition, a further part of the export gas is qualitatively improved by the CO 2  separation apparatus, so as to generate a high-quality reduction gas which can be supplied for metallurgical use.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional under 37 C.F.R. §1.53(b) of, andclaims priority to, prior U.S. Pat. No. 8,834,599, issued Sep. 16, 2014(U.S. patent application Ser. No. 13/125,691, filed Aug. 10, 2011),which is a national phase conversion of PCT/EP2009/062607 filed Sep. 29,2009, which claims priority to Austrian Application No. A 1658/2008filed Oct. 23, 2008. The contents of which are hereby incorporated byreference in their entirety.

TECHNICAL FIELD

The invention relates to a method for operating a melt reductionprocess, in particular with a blast furnace or with a melting assemblyand at least one reduction assembly, batch materials being reduced bymeans of a reduction gas, using carbon carriers and, if appropriate,aggregates, and being melted into pig iron or steel semifinishedproducts, and the reacted reduction gas being diverted as top gas andbeing discharged, purified, as export gas.

BACKGROUND

The invention relates, further, to an apparatus for operating a meltreduction process, with a blast furnace or with a melting assembly andat least one reduction assembly, batch materials being reducible bymeans of a reduction gas, using carbon carriers and, if appropriate,aggregates, and being meltable into pig iron or steel semifinishedproducts, and the reacted reduction gas being divertible as top gas and,purified, if appropriate mixed with purified and cooled excess gas fromthe melting assembly, being dischargeable as export gas.

It is known from the prior art that process gases, such as, for example,top gas from melt reduction devices, or a mixture of residual gases aretreated in other processes and plants, the thermal and chemical energyof the top gas often being utilized. Problems are a fluctuating gascomposition and the low export gas pressure downstream of the scrubbersystems, which make a more efficient treatment of the export gasesdifficult. Further, it is known that the export gas or pure top gas isemployed in turbines for the generation of kinetic energy (expansionturbines) and heat (gas turbines). Here, too, there is the problem that,on account of the low pressure, the low calorific value after theadmixture of residual gas from a CO.sub.2 removal plant and thecalorific value fluctuations, the export gas can be used only in adisadvantageous way in a gas turbine or a combined-cycle power station.

SUMMARY

According to various embodiments, a method and an apparatus can beprovided which give rise to a better and more efficient utilization ofthe process gases and an overall improved energy balance in the linkbetween a melt reduction process and export gas utilization, forexample, by a gas turbine or a combined-cycle power station.

According to an embodiment, in a method for operating a melt reductionprocess, in particular with a blast furnace or with a melting assemblyand at least one reduction assembly, batch materials being reduced bymeans of a reduction gas, using carbon carriers and, if appropriate,aggregates, and being melted into pig iron or steel semifinishedproducts, and the reacted reduction gas being diverted as top gas and,purified, if appropriate mixed with purified and cooled excess gas fromthe melting assembly, being discharged as export gas, wherein at leastpart of the export gas is utilized thermally in a gas turbine, and theexhaust gas from the gas turbine is used in waste heat steam generationfor generating steam, at least a further part of the export gas beingsupplied to a device for the separation of CO.sub.2, and the tail gasfrom this device being burnt in waste heat steam generation for theadditional generation of steam.

According to a further embodiment, the top gas can be drawn off from theblast furnace or from the reduction assembly. According to a furtherembodiment, part of the export gas is first compressed, cooled and thensupplied to the device for the separation of CO.sub.2. According to afurther embodiment, the export gas can be compressed in a fuel gascompressor before combustion in the gas turbine. According to a furtherembodiment, part of the export gas can be supplied to an expansionturbine, and it is expanded, along with a pressure reduction, and issubsequently admixed to the tail gas. According to a further embodiment,the tail gas, if appropriate after mixing with export gas, can beintermediately stored, before its combustion in the waste heat steamgeneration, in a storage device for the compensation of calorific valuefluctuations. According to a further embodiment, the export gas can bededusted before its combustion in the gas turbine. According to afurther embodiment, metallurgical gases and/or natural gas and/ornitrogen and/or water vapor or mixtures thereof can be added for thecompensation of calorific value fluctuations or for adapting thecalorific value in the export gas before its combustion in the gasturbine. According to a further embodiment, the export gas can bebuffered in a buffer device before its combustion in the gas turbine, inorder to ensure an equalization of the export gas quantity or export gascalorific value. According to a further embodiment, the steam generatedin the waste heat steam generation can be supplied to a steam turbine.According to a further embodiment, the device for the separation ofCO.sub.2 may operate on the basis of a pressure change or vacuumpressure change method, in particular according to the adsorptionprinciple. According to a further embodiment, only export gas with amean calorific value >4000 kJ/Nm.sup.3, in particular >5000 kJ/Nm.sup.3,can be supplied to the gas turbine. According to a further embodiment,the calorific value of the export gas can be determined online.According to a further embodiment, the fraction of the export gas whichis supplied to the gas turbine may amount to 30 to 90% of the top gas.According to a further embodiment, the blast furnace can be operatedwith an oxygen-containing gas, in particular with an oxygenfraction >70%, particularly preferably >80%. According to a furtherembodiment, at least part of the export gas purified in the device forthe separation of CO.sub.2 can be introduced, if appropriate afterheating, into the blast furnace or the reduction assembly. According toa further embodiment, at least part of the tail gas or gas mixtures withtail gas may be burnt in a heating device, with the addition of airand/or oxygen, the waste heat being used for heating the purified exportgas before it is introduced into the blast furnace.

According to another embodiment, an apparatus for operating a meltreduction process as described above, may comprise a blast furnace or amelting assembly and at least one reduction assembly, batch materialsbeing reducible by means of a reduction gas, using carbon carriers and,if appropriate, aggregates, and being meltable into pig iron or steelsemifinished products, and the reacted reduction gas being divertible astop gas and, purified, if appropriate mixed with purified and cooledexcess gas from the melting assembly, being dischargeable as export gas,wherein a gas turbine with a generator for the thermal reaction of atleast part of the export gas is provided and waste heat steamgeneration, in which steam can be generated by means of the hot exhaustgases from the gas turbine, is provided, and a device for the separationof CO.sub.2 is provided, to which at least part of the remaining exportgas can be supplied, so as to form a gas purified of CO.sub.2 and a tailgas, and a storage device for the absorption and compensation ofcalorific value fluctuations in the tail gas is provided, the storagedevice being connected to the waste heat steam generation which has aheating device for the combustion of the tail gas in order to formsteam.

According to a further embodiment of the apparatus, a steam turbine witha generator for expanding the steam which has occurred in the waste heatsteam generation is provided. According to a further embodiment of theapparatus, a buffer device for storing the export gas before it issupplied to the gas turbine is provided, so that the export gas quantitysupplied to the gas turbine or the export gas calorific value can bekept uniform. According to a further embodiment of the apparatus, thebuffer device may have a measuring device for measuring the calorificvalue of the export gas, while, based on the measurement, metallurgicalgas and/or natural gas and/or nitrogen and/or water vapor can besupplied in order to adapt the calorific value. According to a furtherembodiment of the apparatus, a filter, in particular an electrostaticfilter, for purifying the export gas before its compression and supplyto the gas turbine may be provided. According to a further embodiment ofthe apparatus, a compressor for the pressure rise and/or a cooler forcooling the remaining part of the export gas before it is supplied tothe device for the separation of CO.sub.2 can be provided. According toa further embodiment of the apparatus, a fuel gas compressor forcompressing the export gas before it is supplied to the gas turbine canbe provided. According to a further embodiment of the apparatus, anexpansion turbine for utilizing the pressure energy of the export gascan be provided, in which case the expanded export gas can be suppliedto the storage device via a line. According to a further embodiment ofthe apparatus, a preheating device heatable by means of tail gas can beprovided for heating the export gas purified of CO.sub.2, so that theheated purified export gas can be supplied to the blast furnace.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a process diagram of a melt reduction process with a blastfurnace operated by oxygen.

FIG. 2 shows a process diagram of a melt reduction process with a meltreduction plant according to COREX.RTM. (agglomerate ore) or FINEX.RTM.(fine ore).

DETAILED DESCRIPTION

According to various embodiments, at least part of the export gas isutilized thermally in a gas turbine. The exhaust gas from this gasturbine is used in waste heat steam generation for generating steam. Afurther part of the export gas is supplied to a device for theseparation of CO.sub.2 and/or to the low-pressure export gas system, thetail gas which in this case occurs, that is to say the residual gasoccurring due to the separation of the CO.sub.2, being supplied to wasteheat steam generation and being burnt for the additional generation ofsteam. As a result, on the one hand, the quality of the export gas isimproved by the device for the separation of CO.sub.2, and in this casethe reduction potential of the export gas, that is to say its fractionof reducing components, is raised or a high-grade reduction gas isgenerated which can be supplied for metallurgical use. On the otherhand, combustible fractions of the tail gas are supplied for thermalutilization, so that the energy balance is improved. It is in this caseadvantageous that the export gas, which has a higher pressure and ahigher fraction of combustible components, is treated separately fromthe tail gas. Consequently, the quality of the export gas which is burntin the gas turbine is not diminished by the tail gas, and thereforecomplicated pressure rises or else a lower energy output in the gasturbine are avoided. In particular, calorific value fluctuations, suchas are unavoidable due to the process in the tail gas in the case ofdevices for the separation of CO.sub.2, especially when CO.sub.2separation by means of adsorption methods is used, no longer presentproblems for the gas turbine. The efficient operation of gas turbinespresupposes a fuel gas having a largely uniform calorific value, so thatonly advantages arise in the gas turbine due to a separate processing ofthe tail gas.

Since the reduction gas quantity from the melt gasifier is not uniform,a regulating gas quantity, what is known as excess gas, has to be lockedout as export gas. The quantity of excess gas arises from as uniform areduction gas quantity as possible required in the reduction assemblyand from a regulation of the system pressure in the melting assembly.

According to an embodiment, the top gas is drawn off from the blastfurnace or from the reduction assembly. In addition to a part streambeing used in CO.sub.2 separation, the export gas can be supplied to agas turbine, and therefore the energy balance of the link between a meltreduction process and a gas turbine or waste heat steam generation canbe markedly improved.

The purification of the top gas may take place by means of dryseparation, in particular gravity separation, and/or wet separation. Thetop gas is mostly dust-laden, and therefore the dusts and fine solidparticles have to be separated. Dry separation in this case affords theadvantage that there is no sharp cooling of the top gas. If there arevery stringent requirements as to the gas quality, an essentiallycomplete removal of the dusts and solid particles may take place bymeans of wet dedusting, in which case this may follow dry dedusting ormay also be used alone. Wet dedusting results in a sharp cooling of thetop gas. The dry-purified or wet-purified top gas is designated asexport gas and can then be supplied for utilization in a turbine.

According to various embodiments, the remaining part of the export gasis first compressed, cooled and then supplied to the device for theseparation of CO.sub.2. As a result of the pressure rise and thecooling, the process conditions for the separation of CO.sub.2 can beadapted or improved.

According to an embodiment, the export gas is compressed in a fuel gascompressor before combustion in the gas turbine. The gas turbine canconsequently be set at an economically optimal operating point and theefficiency can be increased.

According to an embodiment, part of the export gas is supplied to anexpansion turbine, and it is expanded, along with a pressure reduction,and is subsequently admixed to the tail gas. By virtue of this measure,for example in the event of a surplus of export gas because the gasturbine can no longer process it, the pressure energy can first beutilized, the export gas being expanded. The turbine may be coupled to agenerator for the generation of current. The expanded export gas issubsequently admixed to the tail gas, the fraction of combustiblecomponents rising overall.

According to an embodiment, the tail gas, if appropriate after mixingwith export gas, is intermediately stored, before its combustion in thewaste heat steam generation, in a storage device for the compensation ofcalorific value fluctuations. As a consequence of the process, thedevice for the separation of CO.sub.2 generates a tail gas which hasgreatly varying calorific values, the fluctuations occurring with highfrequency, that is to say occurring only briefly in time and largelybeing compensated reliably over a longer period. Thus, by means ofcompensation in intermediate storage, a virtually equalized calorificvalue can be set and sharp fluctuations in combustion can be avoided. Byexport gas being admixed to the tail gas, the calorific value can befurther adapted.

In an embodiment, the export gas is dedusted before its combustion inthe gas turbine. The additional dedusting can ensure that no damage inthe turbine can be caused by residual dusts.

In a further an embodiment, metallurgical gases and/or natural gasand/or nitrogen and/or water vapor or mixtures thereof are added for thecompensation of calorific value fluctuations or for adapting thecalorific value in the export gas before its combustion in the gasturbine. Gas turbines require as uniform a heating power as possible anda uniform calorific value for stable operation. Fluctuations in theoperation of the melt reduction process give rise to changes in thecomposition, so that, as a result of the introduction according tovarious embodiments of metallurgical gas, such as, for example, cruciblegases or coke oven gases, available in sufficient quantities inmetallurgical plants, or of other suitable combustible gases, thecalorific value can, as required, be increased or, by the admixing ofnitrogen, be lowered, so that stable conditions for the gas turbine canbe ensured. The use of waste nitrogen from an air separation plant isparticularly cost-effective.

According to an embodiment, the export gas is buffered in a bufferdevice before its combustion in the gas turbine, in order to ensure anequalization of the export gas quantity. By virtue of the measuredescribed, a highly stable operation of the gas turbine can be ensured.

According to an embodiment, the steam generated in the waste heat steamgeneration is supplied to a steam turbine. By the steam formed in thewaste heat steam generation being utilized, the efficiency of theprocess can be markedly increased.

According to an embodiment, the device for the separation of CO.sub.2operates on the basis of a pressure change or vacuum pressure changemethod, in particular on an adsorption basis. Methods of this type aredistinguished by high separation rates, so that the purified export gashas a high reduction potential and can be utilized anew in the meltreduction process, with the result that the quantity of CO.sub.2generated per tonne of pig iron can be reduced.

According to an embodiment, only export gas with a mean calorificvalue >4000 kJ/Nm.sup.3, in particular >5000 kJ/Nm.sup.3, is supplied tothe gas turbine. Control via the calorific value of the export gas canensure that the gas turbine achieves a high efficiency, while thededusting, the buffer device and the fuel gas compressor can havesmaller dimensioning, since export gas with too low a calorific valuedoes not have to be supplied to the turbine via these devices. Morecost-effective components up to and including the gas turbine aretherefore obtained. Further, as a result, the energy loss due to theotherwise necessary compression of CO.sub.2-rich tail gas and to asubsequent expansion in the gas turbine is avoided.

According to a further embodiment, the calorific value of the export gasis determined online. By the determination of the calorific value beingcarried out online, it is possible to regulate the calorific valuecontinuously, in particular by the admixture of combustible gases ornitrogen, thereby making an even more stable operation of the gasturbine possible.

According to a further embodiment, the fraction of the export gas whichis supplied to the gas turbine amounts to 30 to 90% of the top gas. Onthe basis of this quantity, on the one hand, a utilization of thecombustible components of the export gas is possible, while sufficientexport gas can still be supplied to the device for the separation ofCO.sub.2, so that utilization in the melt reduction process is possible.The fractions may also be adapted, as required, for example if moreexport gas is to be recirculated in the melt reduction process.

According to a further embodiment, the blast furnace is operated with anoxygen-containing gas, in particular with an oxygen fraction >70%,particularly preferably >80%. By virtually pure oxygen being used foroperation, the quality of the process gas during reduction, but alsothat of the top gas, are increased, so that there is a higher fractionof reducing or combustible components. The melt reduction process in theblast furnace and the thermal utilization of the export gas canconsequently be improved.

According to a further embodiment, at least part of the export gaspurified in the device for the separation of CO.sub.2 is introduced, ifappropriate after heating, into the blast furnace or the reductionassembly. The export gas thus purified has a high reduction potentialand can therefore be used anew for reducing the batch materials, sothat, for example, the quantity of carbon carriers in the blast furnaceor in the reduction assembly can be reduced. Conventional batchmaterials are in this case iron ores, agglomerated iron ore carriers(pellets, sinter), iron ore concentrates and, in addition, carboncarriers and aggregates.

According to a further embodiment, at least part of the tail gas or gasmixtures with tail gas is burnt in a heating device, with the additionof air and/or oxygen, the waste heat being used for heating the purifiedexport gas before it is introduced into the blast furnace. The exportgas can consequently be heated cost-effectively in order to set the gastemperature necessary for introduction.

The apparatus according to various embodiments for operating the meltreduction process has a blast furnace or a melting assembly and at leastone reduction assembly, batch materials being reduced by means of areduction gas, using carbon carriers and, if appropriate, aggregates,and being melted into pig iron or steel semifinished products. Thereduction gas reacted in the melt reduction process is diverted as topgas and, purified, if appropriate mixed with purified and cooled excessgas from the melting assembly, is discharged as export gas. Further, agas turbine with a generator for the thermal reaction of at least partof the export gas and waste heat steam generation are provided, in thelatter of which steam can be generated by means of the hot exhaust gasesfrom the gas turbine. The apparatus according to various embodiments hasa device for the separation of CO.sub.2, to which the at least part ofthe remaining export gas can be supplied, so as to form a gas purifiedof CO.sub.2 and a tail gas, and a storage device for the absorption andcompensation of calorific value fluctuations in the tail gas, thestorage device being connected to the waste heat steam generation whichhas a heating device for the combustion of the tail gas in order to formsteam. By means of the apparatus according to various embodiments, theexport gas, which has a high pressure and a high calorific value, can beprocessed separately from the tail gas which has a low pressure and alower calorific value. Consequently, although the quantity of high-gradeexport gas is smaller, the latter is distinguished by the higherpressure and the higher calorific value, so that its utilization in thegas turbine can take place more efficiently. As a result of the separatecombustion of the tail gas in the heating device of the waste heat steamgeneration, the energy of the combustible components in the tail gas canbe utilized. According to an embodiment, a steam turbine with agenerator for expanding the steam which has occurred in the waste heatsteam generation is provided. Owing to the utilization of the waste heatfrom the hot exhaust gas of the gas turbine and of the waste heat fromthe combustion of the tail gas, the energy efficiency of the process canbe increased, while the steam turbine can be used for current generationby being coupled to a generator.

To purify the top gas, a dry separation device, in particular gravityseparation and/or a wet separation device may be provided. The requiredpurity of the export gas can consequently be set, dry separation havingthe advantage of only slight cooling of the top gas.

According to a further embodiment, a buffer device for storing theexport gas before it is supplied to the gas turbine is provided, so thatthe export gas quantity supplied to the gas turbine or the export gascalorific value can be kept uniform.

According to a further embodiment, the buffer device has a measuringdevice for measuring the calorific value of the export gas, while, basedon the measurement, metallurgical gas and/or natural gas and/or nitrogenand/or water vapor can be supplied in order to adapt the calorificvalue. By means of online measurement, a regulation of the calorificvalue or of the export gas quantity can be implemented, while thequantity of export gas or of admixed metallurgical gas and/or nitrogencan be set by means of actuating members, such as, for example,regulating valves.

According to a further embodiment, a filter, in particular anelectrostatic filter, for purifying the export gas before it is suppliedto the gas turbine is provided. This fine filtration, if appropriateafter a preceding dust filtration in the top gas, ensures that the gasturbine is not subjected to abrasive or mechanical load and even thefinest dusts are separated.

According to a further embodiment, a compressor for the pressure riseand/or a cooler for cooling the remaining part of the export gas beforeit is supplied to the device for the separation of CO.sub.2 are/isprovided. This is necessary in order, via an appropriate adaptation ofthe temperature and pressure, to allow optimal operation of the devicefor the separation of CO.sub.2 and subsequent utilization as reductiongas.

According to a further embodiment, a fuel gas compressor for compressingthe export gas before it is supplied to the gas turbine is provided. Thecharging of the gas turbine can consequently take place at the pressurelevel coordinated with the gas turbine.

According to a further embodiment, an expansion turbine for utilizingthe pressure energy of the export gas is provided, in which case theexpanded export gas can be supplied to the storage device via a line.Thus, the pressure energy can first be utilized before the export gas ismixed with the tail gas in the storage device. The expansion turbine maybe coupled to a generator for current generation.

According to a further embodiment, a preheating device heatable by meansof tail gas is provided for heating the export gas purified of CO.sub.2,so that the heated purified export gas can be supplied to the blastfurnace. Due to the combustion of the tail gas in the heating device, itis possible to heat the purified export gas cost-effectively before itis recirculated into the blast furnace.

FIG. 1 shows a blast furnace 1 which is fed with oxygen via the ringline 2. The top gas is supplied via a top gas discharge line 3 to a dryseparation device 4 and, if appropriate, also to a wet separation device5, the dust-laden top gas giving rise to the export gas which isdischarged via the line 6. By means of a delivery line 7 to the devicefor the separation of CO.sub.2 8, part of the export gas is supplied bymeans of a compressor 9 and a cooler 10 to the device for the separationof CO.sub.2 8, an export gas purified of CO.sub.2, which is alsodesignated as recycle gas, and a tail gas then being formed, which aredischarged via the recycle gas line 11 and the tail gas line 12 and 13respectively. The tail gas line 13 issues in a storage device 14 forreceiving the tail gas, calorific value compensation occurring in thestored tail gas. By means of tail gas delivery lines 15 a, 15 b, thepreviously stored tail gas can then be supplied to a waste heat steamgenerator 16. Here, as a result of the combustion of the tail gas, steamis generated which drives a steam turbine 17 and a generator 18, currentbeing generated.

In a special type of operation of the method according to variousembodiments, the tail gas may also be utilized for heating the recycledexport gas, the tail gas being supplied to a preheating device 19 inwhich the tail gas is burnt and recycle gas is heated, the heatedrecycle gas then being introduced into the blast furnace 1 via adelivery line 20. The preheating device may in this case even bebypassed and the recycle gas be introduced directly into the blastfurnace via a delivery line 20 a. In addition to the use of the exportgas for producing recycle gas, the export gas serves, above all, as anenergy carrier, and in this case the chemical energy and the pressureenergy can be utilized. The export gas is supplied to a buffer device 21and a filter 22. Here, on the one hand, the regulation of as uniform anexport gas quantity as possible and the regulation of as uniform acalorific value as possible take place, the latter being set by theaddition of metallurgical gas or nitrogen. For this purpose, thecalorific value of the export gas is measured online in the bufferdevice, and the calorific value is raised by the addition ofmetallurgical gas or natural gas or is lowered by the addition ofnitrogen or water vapor.

The export gas thus treated is added via a fuel gas compressor 23 to thecombustion chamber of a gas turbine 24 which, in turn, drives agenerator 25. The hot exhaust gas which in this case occurs is suppliedvia exhaust gas lines 26 to the waste heat steam generation 16 in orderto generate steam, the steam, in turn, being processed in the steamturbine 17.

Alternatively, part of the export gas or even the predominant part ofthe export gas may be supplied to an expansion turbine 27, this turbinebeing coupled to a generator, not illustrated. The expanded export gascan then be supplied to the storage device 14 in which the expandedexport gas is then mixed with the tail gas.

FIG. 2 shows a plant or process diagram similar to FIG. 1, and thereforeidentical components have been designated by the same referencenumerals. Instead of the blast furnace, the melt reduction process iscarried out in a melting assembly 28 and at least one reduction assemblyR. In the concrete example, 4 series-connected reduction assemblies R1,R2, R3 and R4 are arranged, which use a reduction gas formed in themelting assembly in order to reduce the batch materials, in particulariron ore, agglomerated iron ore carriers (pellets, sinter) or oreconcentrates. The melting assembly 28 is advantageously designed as amelt gasifier. The reduction assemblies are routed in countercurrent tothe batch materials and, after use in the reduction assemblies, aredrawn off as top gas at the last reduction assembly R4 and purified in awet separation device 5. The then purified top gas can be supplied, in asimilar way to the description of FIG. 1, as export gas to the gasturbine 23 or to the device for the separation of CO.sub.2 8. The tailgas is, in turn, supplied to the storage device 14 via the tail gas line12. The purified export gas, which is also designated as recycle gas,can be supplied to the generator gas dedusting device 29 via the recyclegas line 11. In the generator gas dedusting device 29, the generator gasgenerated in the melting assembly 28, using carbon carriers, is dedustedand is supplied as process gas or as reduction gas to the reductionassembly R1. The material at least partially reduced in the reductionassemblies is designated as low reduced iron (LRI) and, afteragglomeration, is introduced into the melting assembly 28 where it isthen melted into pig iron or into steel semifinished products.

LIST OF REFERENCE SYMBOLS

-   1 Blast furnace-   2 Gas ring line-   3 Top gas discharge line-   4 Dry separation device-   5 Wet separation device-   6 Line-   7 Delivery line-   8 Device for the separation of CO.sub.2-   9 Compressor-   10 Cooler-   11 Recycle gas line-   12 Tail gas line-   13 Tail gas line-   14 Storage device-   15 a, 15 b Tail gas delivery lines-   16 Waste heat steam generator-   17 Steam turbine-   18 Generator-   19 Preheating device-   20, 20 a Delivery line-   21 Buffer device-   22 Filter-   23 Fuel gas compressor-   24 Gas turbine-   25 Generator-   26 Exhaust gas lines-   27 Expansion turbine-   28 Melting assembly-   29 Generator gas dedusting device

What is claimed is:
 1. An apparatus for operating a melt reductionprocess, comprising: a blast furnace or a melting assembly, at least onereduction assembly that a) receives batch materials that are reducibleby means of a reduction gas, using carbon carriers and, if appropriate,aggregates, and are meltable into pig iron or steel semifinishedproducts, and b) produces reacted reduction gas that is suitable as topgas, purified, and if appropriate, mixed with purified and cooled excessgas from the melting assembly and discharged as export gas, a gasturbine with a generator for the thermal reaction of at least part ofthe export gas, a waste heat steam generator, in which steam can begenerated by means of hot exhaust gases from the gas turbine, a devicefor the separation of CO₂, to which at least part of a remainder of theexport gas can be supplied, so as to form a gas purified of CO₂ and atail gas, and a storage device for the absorption and compensation ofcalorific value fluctuations in the tail gas, the storage device beingconnected to the waste heat steam generator which has a heating devicefor the combustion of the tail gas in order to form steam.
 2. Theapparatus according to claim 1, further comprising a steam turbine witha generator for expanding the steam from the waste heat steam generator.3. The apparatus according to claim 1, further comprising a bufferdevice for storing the export gas before it is supplied to the gasturbine to keep the export gas quantity supplied to the gas turbine orthe export gas calorific value uniform.
 4. The apparatus according toclaim 3, wherein the buffer device has a measuring device for measuringthe calorific value of the export gas, and wherein based on themeasurement, the calorific value can be adapted by supplying at leastone of metallurgical gas, natural gas, nitrogen, and water vapor.
 5. Theapparatus according to claim 1, further comprising a filter or anelectrostatic filter for purifying the export gas before its compressionand supply to the gas turbine.
 6. The apparatus according to claim 1,further comprising at least one of a compressor for increasing pressure,and a cooler for cooling, the remainder of the export gas before it issupplied to the device for the separation of CO₂.
 7. The apparatusaccording to claim 1, further comprising a fuel gas compressor forcompressing the export gas before it is supplied to the gas turbine. 8.The apparatus according to claim 1, further comprising an expansionturbine for utilizing energy of the export gas and producing expandedexport gas supplied to the storage device via a line.
 9. The apparatusaccording to claim 1, further comprising a preheating device heatable bymeans of tail gas for heating the export gas purified of CO₂, so thatthe heated purified export gas can be supplied to the blast furnace.